Synthesis is an incredibly challenging concept to define in simple terms. Entire volumes have been written about the process, the concept and the various methods that can be used to engage in the activity. It is not the intention of this chapter to provide an in-depth analysis of synthesis as an intellectual activity; however, this is a component of the literature review process that consistently challenges students and researchers. It also happens to be the step in the review process that produces the most value – that is, the synthesis is where the findings from all of the searching, reading and analysis results come together. Therefore, one must not gloss over the approach to synthesis, and understanding the various methods that can be used is an important consideration. In this chapter, the concept of synthesis will be defined in straightforward terms, and various methods will be introduced, with examples offered, and further reading suggested.

Definition:

Combining parts into a newly conceived whole is crucial to synthesis. Observations made from distinct pieces, and then assembled into an entirely new perspective is how synthesis is generated.

Imagine a researcher who is studying play based learning in kindergarten. They have amassed a collection of articles on the topic, and have done their reading. Based on the conclusions from these studies, they have summarized the findings:

• One study found that teachers in Ontario believed that play-based learning (PBL) led to increased social inclusion of children with neurodevelopmental delay (NDD).
• One study found that a play-based training programme for parents in Hong Kong increased the social skills of their children
• One study found that an outdoor play-based learning curriculum in Wales led to increased involvement in tasks and deeper learning when children perceived their lessons as play
• One study looked to determine where children would choose to focus their play when given choices of stations; results showed that stations that promoted physical activity were given preference, indicating that when available, children will choose more active play than stationary.
• One study found that when play stations encouraged children to write, authentic opportunities for creative expression resulted, but only when intentional teaching took place concurrently

The above list is not a synthesis. It is simply a summary of the findings from distinct studies that have very loose connections. It is now the job of the researcher to try to make connections that may form a cohesive new interpretation of what these other researchers have concluded. This is the process of integration. What are some potential observations that could be made about the above studies?

• Play-based learning increased inclusion in the classroom
• Participation of adults (both teachers and parents) have measurable effects on outcomes
• Play-based learning is effective for learning
• Play-based learning is a global practice

None of the example studies drew these conclusions, nor was it the intent of those studies to draw those conclusions. Rather, by analyzing the findings of studies done in very specific circumstances, the intellectual exercise of synthesis allows the researcher to make higher level observations based on the similarities (i.e. they all focus on play based learning) and differences (i.e. they each focus on different participants in different circumstances) in a critical mass of studies that share many similar characteristics, but are not – strictly speaking – specifically about the same thing.

Approaches to Synthesis

There is a great deal of flexibility and individual choice around approaches to synthesis.  As stated earlier, this section is not meant to be an exhaustive exploration of the varieties of methods and techniques available; rather, some general guidelines for consideration.

Quite broadly, as described by Booth (2012), synthesis relies on pattern recognition in the data.  Key considerations would include the comparability of the study settings and the interventions – “in short…whether…it makes sense to treat all included studies as a group (lumping) or whether they make more sense as a series of separate and distinct groups (splitting)” (p. 179).

A common approach to synthesis includes narrative approaches which summarize the characteristics and findings of a body of research, primarily using words and text (Booth, 2012).  Tabulation can also be used in synthesis; providing a chart of the relevant data points – “eyeballing patterns across rows or down columns.” (p.185).

Examples:

Thematic analysis is a popular choice, which uses ‘codes’ or ‘themes’ that may be pre-specified or emergent from the data (Gough, 2017). The data is then mapped to these themes and codes in a consistent manner. This approach is common when the synthesis is focussed on qualitative studies.

See it in use here:

Sartain, S. A., Stressing, S., & Prieto, J. (2015). Patients’ views on the effectiveness of patient-held records: A systematic review and thematic synthesis of qualitative studies. Health Expectations, 18(6), 2666–2677. https://doi.org/10.1111/hex.12240

An alternative approach to a narrative or thematic approach is a meta-analysis, which uses a set of statistical procedures to integrate, summarize or organize a set of reported statistical findings of studies that investigate the same research question using the same methods of measurement.” (Booth, 2012)  This methodology is appropriate when there are homogenous amounts of quantitative data under consideration.

See it in use here:

Ettehad, D., Emdin, C. A., Kiran, A., Anderson, S. G., Callender, T., Emberson, J., Chalmers, J., Rodgers, A., & Rahimi, K. (2016). Blood pressure lowering for prevention of cardiovascular disease and death: a systematic review and meta-analysis. Lancet (London, England), 387(10022), 957–967. https://doi.org/10.1016/S0140-6736(15)01225-8

Evidence Synthesis Chart

Creating an evidence synthesis chart will assist you by compiling and presenting the relevant data points to assist with observing the patterns in the data.

Take an article that you’re already familiar with, and practice extracting data into the evidence synthesis chart provided.

Barnett-Page, E., & Thomas, J. (2009). Methods for the synthesis of qualitative research: A critical review. BMC Medical Research Methodology, 9(1), 59.

Booth, A., Papaioannou, D., & Sutton, A. (2012). Systematic approaches to a successful literature review. Sage.

Gough, D., Oliver, S, & Thomas, J. (2017). An Introduction to Systematic Reviews. Sage.

Strike K & Posner G. (1983). Types of synthesis and their criteria. In Ward, S & L. Reed (Eds.), Knowledge structure and use: implications for synthesis and interpretation (pp. 343-362). Temple University Press.